Liquid crystalline polymer composition

ABSTRACT

Liquid crystalline polymer having repeat units derived from 4,4′-biphenol, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and 4-hydroxybenzoic acid in a limited compositional range have melting points of 400° C. or more, and are useful for molded articles and for films, particularly for uses where good high temperature resistance is needed.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/434,263, filed Dec. 18, 2002.

FIELD OF THE INVENTION

[0002] A liquid crystalline polymer having repeat units derived from4,4′-biphenol, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and4-hydroxybenzoic acid in a selected limited compositional range hasexcellent high temperature properties.

TECHNICAL BACKGROUND

[0003] Liquid crystalline polymers (LCPs) are commercially sold for avariety of uses, and in many cases they have (combinations of)properties that can't be matched by other polymers. Many LCPs have goodhigh temperature properties that are useful, for example from about 250°C. to about 320° C. There are other LCPs that have been claimed to beuseful at higher temperatures, but these have often had other drawbacks,such as poor processability and/or poor thermal stability at their meltprocessing and/or use temperatures. There fore LCPs with improved hightemperature properties are of interest. Described herein are such LCPs,which contain repeat units derived from 4,4′-biphenol, terephthalicacid, 2,6-naphthalenedicarboxylic acid, and 4-hydroxybenzoic acid in aselected limited compositional range.

[0004] U.S. Pat. No. 4,849,499 describes copolymers containing therepeat units described above. None of the polymers actually made arereported to have melting points above 400° C., and the compositionalranges described herein are not mentioned.

[0005] Japanese Patent 7-47624B2 describes polymers with the repeatunits derived from 4,4′-biphenol, terephthalic acid,2,6-naphthalenedicarboxylic acid, and 4-hydroxybenzoic acid. Althoughthe compositional range described in this patent overlaps with thecompositional range of this invention, no examples within the range ofthis invention are reported, and all polymers actually made have a “flowinitiation temperature” below 320° C., and are reported to be liquids at320° C.

[0006] Working Example 1 of Japanese Patent Application 8-41187 reportsthe preparation of an LCP derived from 4,4′-biphenol, terephthalic acid,2,6-naphthalenedicarboxylic acid, and 4-hydroxybenzoic acid and having amelting point of 387° C. The compositional range of this LCP is outsidethe compositional range claimed herein.

SUMMARY OF THE INVENTION

[0007] This invention concerns a composition, comprising, a liquidcrystalline polymer consisting essentially of repeat units of theformula

[0008] wherein per 100 molar parts of (I), (II) is 85-98 molar parts,(III) is 2-15 molar parts, and (V) is 100 to 210 molar parts,

[0009] provided that:

[0010] the molar ratio of (I)/(II)+(III) is about 0.90 to about 1.10;

[0011] when (IV) is 175 or more molar parts, (III) is about 2 to 10molar parts; and

[0012] a melting point of said liquid crystalline polymer is 400° C. ormore.

DETAILS OF THE INVENTION

[0013] In these polymers (I) is derived from 4,4′-biphenol, (II) isderived from terephthalic acid, (III) is derived from2,6-napthtalenedicarboxylic acid, (IV) is derived from 4-hydroxybenzoicacid, or one or more of their respective reactive derivatives.

[0014] In a preferred LCP, (II) is about 3 to about 10 molar parts andmore preferably 3 to about 8 molar parts, and/or (III) is about 90 toabout 97 molar parts and more preferably about 93 to about 97 molarparts, and/or (IV) is about 100 to about 200 molar parts, morepreferably about 100 to about 175 molar parts, and most preferably about100 to about 160 molar parts. Also, preferably the molar ratio of(I)/(II)+(III) is about 0.95 to about 1.05 and more preferably about0.98 to about 1.02. Any of these preferred compositional ranges may becombined with any of the other preferred compositional ranges.

[0015] The LCP preferably has a melting point of about 410° C. or more.The melting point is taken as the peak of the melting endotherm on thesecond heat when measured by Differential Scanning Calorimetry accordingto ASTM Method D3418-82, using a heating rate of 25° C./min. By “secondheat” is meant the LCP is heated from room temperature at 25° C./min toabove the melting point, cooled at 25° C./min to about 200° C., thenheated again at 25° C./min to above the melting point. The melting pointof the second heat is taken during the second melting of the LCP.

[0016] The LCPs can be made by any conventional method of makingaromatic polyester LCPs. A typical process for producing such LCPsinvolves mixing 4,4′-biphenol, terephthalic acid,2,6-naphthalenedicarboxylic acid, and 4-hydroxybenzoic acid with enoughof a carboxylic acid anhydride such as acetic anhydride to acylate thehydroxyl groups of the 4,4′-biphenol and 4-hydroxybenzoic acid, and thenheating the resulting mixture to remove byproduct carboxylic acid.Alternatively, the desired ester may be formed beforehand and added tothe polymerization vessel, and the polymerization run without additionof carboxylic acid anhydride. The polymerizing mixture is eventuallyheated to a relatively high temperature, typically in the latter stagesunder vacuum, to produce the final LCP. This is done while the processmixture is a liquid (in the melt). However if, as in the present case,the melting point of the final desired LCP is very high, it may bedifficult to heat the mixture to such a high temperature (above themelting point). In such a situation, before the LCP is fully formed (themolecular weight has reached the desired level) the liquid is cooled andsolidified, and broken into small particles. These particles are thenheated while in the “solid state” under stream of inert gas such asnitrogen or under a vacuum to raise the molecular weight to the desiredlevel. This latter part of the process is commonly known as solid statepolymerization (SSP), see for instance F. Pilati in G. Allen, et al.,Ed., Comprehensive Polymer Science, Vol. 5, Pergamon Press, Oxford,1989, Chapter 13, which is hereby included by reference. For thepolymers of the present invention, SSP is a preferred way of raising themolecular weight to the desired level. Also preferably at least part ofthe SSP process is carried out at a temperature of about 300° C. or moreand more preferably about 320° C. or more.

[0017] It is preferred that the LCP compositions of the presentinvention also comprise 5 to 1000 ppm of an alkali metal cation (asalkali metal cation, not the total of the compound which the alkalimetal cation is a part of), particularly when the LCP is prepared usingSSP (solid state polymerization). The presence of alkali metal cationoften raises the melting point of the LCP formed and/or (when SSP isused in the polymerization process) the color of the resulting LCP islighter. Not included within this 5 to 1000 ppm of alkali metal cationare alkali metal cations which are part of fillers or other similarmaterials, such as glass or mineral fillers, if they are present duringthe SSP. Typically the alkali metal cation will be added as a monomericcompound to the polymerization. It may be the alkali metal salt of acarboxyl containing monomer, such as disodium terephthalate or potassium4-hydroxybenzoate. A preferred method of adding the alkali metal cationis as an alkali metal salt of 4-hydroxybenzoic acid, particularlypotassium 4-hydroxybenzoate. If a hydroxycarboxylic acid is one of themonomers, an alkali metal salt of that compound is a preferred way ofadding the alkali metal cation. Other alkali metal salts may be used,such as lithium acetate. While inorganic salts may be used, they may notbe as effective as organic salts such as alkali metal carboxylates.

[0018] Preferably the alkali metal cation is lithium, sodium orpotassium, more preferably potassium cation. The amount of alkali metalcation is based on the amount of alkali metal cation itself, not thecompound in which it is added. The amount of alkali metal cation in ppmis based on the total amount of LCP in the process. At least 5 ppm,preferably 10 ppm of the alkali metal cation is present. The maximumamount of alkali metal cation is about 1000 ppm, preferably about 100ppm, and most preferably about 40 ppm. Any maximum and minimum preferredamounts of alkali metal cation above can be combined to form a preferredrange of alkali metal cation.

[0019] The LCPs of this invention have melting points of about 400° C.or more, making them useful in applications where good thermalresistance to relatively high temperatures are needed. The LCPs areuseful as molding resins and for films, and can be melt formed intoshaped parts (a part with one or more regular or planned dimensionsand/or shapes) in typical melt forming processes such as injectionmolding, extrusion, and thermoforming.

[0020] In the Examples the following abbreviations are used:

[0021] AA—acetic anhydride

[0022] BP—4,4′-biphenol

[0023] HBA—4-hydroxybenzoic acid

[0024] KHBA—potassium 4-hydroxybenzoate

[0025] N—2,6-naphthtalene dicarboxylic acid

[0026] T—terephthalic acid

[0027] Tm—polymer melting point

EXAMPLES 1-4

[0028] Monomers and acetic anhydride in the molar proportions areindicated in Table 1, and the amounts by weight used are shown in Table2. For Examples 1-3, monomers were weighed out into a 3 L resin kettlefitted with a ground glass top and agitator. A Vigreaux column wasconnected to the ground glass top and the top of the column was fittedwith a reflux splitter, and condenser. After the reactants were charged,the apparatus was connected as described, a nitrogen gas flush wasstarted, and a liquid metal bath heated to 160° C. was raised intoposition to heat approximately 75% of the lower portion of the kettle.At this time, the reflux splitter was adjusted so that 100% of thecondensed vapors were returned to the kettle. The process was operatedwith agitation and 100% reflux for 30 min. Then, the splitter waspartially opened until an estimated 75% of the condensed material wasreturned to the kettle and 25% was removed to a product receiver. Next,the temperature of the metal bath was raised from 160° C. to 330-335° C.over a period of approximately 3 h. The pressure was maintained at oneatmosphere throughout. After the temperature reached 330-335° C., thepressure was maintained at one atmosphere until the stirring motorreached maximum torque. Then, the nitrogen flush was terminated, theagitator was stopped, and the kettle was opened and the product wasremoved from the kettle as a solid.

[0029] Following isolation of the solid materials, each of the materialswas placed in trays in a circulating gas oven for solid statepolymerization to final high molecular weight. Nitrogen was used as thegas in order to exclude air from the oven. The temperature of the ovenwas maintained as follows. Heated as rapidly as possible to 270° C., andheld for 1 h. Then heated as rapidly as possible to 310° C. and held for1 h. Finally, heated to a final temperature of 340° C. and held for 4 h,followed by cooling to room temperature.

[0030] The polymer of Example 4 was prepared in a similar manner exceptthat the reaction vessel was a Hastelloy® metal reactor of approximately19 L internal capacity and a column with packing of hollow glasscylinders was used instead of the Vigreaux column, and the final reactortemperature was 320° C.

[0031] The compositions of the polymers and reactants charged to thevessel are given in Tables 1 and 2 in molar parts and in grams,respectively. Melting points of the polymers are given in Table 2. TABLE1 Ex. BP T N HBA ppm K⁺ 1 100 90 10 200 25 2 100 97 3 150 25 3 100 90 10100 25 4 100 95 5 175 25

[0032] TABLE 2 AA, KHBA, Ex. BP, g T, g N, g HBA, g g gm Tm, ° C. 1281.9 226.3 32.7 418.1 636.7 0.10 406 2 317.8 275.1 11.1 353.6 628.20.10 437 3 358.6 287.9 41.6 266.0 607.4 0.10 425 4 3196 2710 186.1 41506745 10 421

[0033] When an LCP of the composition of Example 2 was made withoutpotassium cation being present the melting point was 424° C., and thecolor of that polymer was darker.

What is claimed is:
 1. A composition, comprising, a liquid crystallinepolymer consisting essentially of repeat units of the formula

wherein per 100 molar parts of (I), (II) is 85-98 molar parts, (III) is2-15 molar parts, and (IV) is 100 to 210 molar parts, provided that: themolar ratio of (I)/(II)+(III) is about 0.90 to about 1.10; when (IV) is175 or more molar parts, (III) is 2 to 10 molar parts; and a meltingpoint of said liquid crystalline polymer is 400° C. or more.
 2. Thecomposition as recited in claim 1 wherein 3 to about 10 molar parts of(II) are present.
 3. The composition as recited in claim 1 wherein 90 to97 molar parts of (III) are present.
 4. The composition as recited inclaim 1 wherein about 100 to about 175 molar parts of (IV) are present.5. The composition as recited in claim 1 wherein 3 to about 10 molarparts of (II) are present, 90 to 97 molar parts of (III) are present,and about 100 to about 175 molar parts of (IV) are present.
 6. Thecomposition as recited in claim 1 wherein said melting point is about410° C. or more.
 7. The composition as recited in claim 1 wherein saidmolar ratio is about 0.95 to about 1.05.
 8. The composition as recitedin claim 1 additionally comprising 5 to about 1000 ppm of an alkalimetal cation.
 9. A shaped part or film of the composition of claim 1.